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PubMed1991

Calcium feedback and sensitivity regulation in primate rods.

Membrane current was recorded from a single primate rod with a suction pipette while the cell was bath perfused with solutions maintained at a temperature of approximately 38 degrees C. A transient inward current was observed at the onset of bright illumination after briefly exposing the outer segment in darkness to Ringer's (Locke) solution containing 3-isobutyl-1-methylxanthine (IBMX), an inhibitor of cGMP phosphodiesterase. After briefly removing external Na+ from around the outer segment in darkness, a similar current was observed upon Na+ restoration in bright light. By analogy to amphibian rods, this inward current was interpreted to represent the activity of an electrogenic Na(+)-dependent Ca2+ efflux, which under physiological conditions in the light is expected to reduce the free Ca2+ in the outer segment and provide negative feedback (the "Ca2+ feedback") to the phototransduction process. The exchange current had a saturated amplitude of up to approximately 5 pA and a decline time course that appeared to have more than one exponential component. In the absence of the Ca2+ feedback, made possible by removing the Ca2+ influx and efflux at the outer segment using a 0 Na(+)-0 Ca2+ external solution, the response of a rod to a dim flash was two to three times larger and had a longer time to peak than in physiological solution. These changes can be approximately accounted for by a simple model describing the Ca2+ feedback in primate rods. The dark hydrolytic rate for cGMP was estimated to be 1.2 s-1. The incremental hydrolytic rate, beta*(t), activated by one photoisomerization was approximately 0.09 s-1 at its peak, with a time-integrated activity, integral of beta*(t)dt, of approximately 0.033, both numbers being derived assuming spatial homogeneity in the outer segment. Finally, we have found that primate rods adapt to light in much the same way as amphibian and other mammalian rods, such as showing a Weber-Fechner relation between flash sensitivity and background light. The Ca2+ feedback model we have constructed can also explain this feature reasonably well.

1-Methyl-3-isobutylxanthine↗
PubMed2006

Integrating haptic-tactile feedback into a video-capture-based virtual environment for rehabilitation.

Video-capture virtual reality (VR) systems are gaining popularity as intervention tools. To date, these platforms offer visual and audio feedback but do not provide haptic feedback. We contend that adding haptic feedback may enhance the quality of intervention for various theoretical and empirical reasons. This study aims to integrate haptic-tactile feedback into a video capture system (GX VR), which is currently applied for rehabilitation. The proposed multi-modal system can deliver audio-visual as well as vibrotactile feedback. The latter is provided via small vibratory discs attached to the patient's limbs. This paper describes the system, the guidelines of its design, and the ongoing usability study.

Computer Simulation↗
PubMed2004

Ultra short-loop feedback control of thyrotropin secretion.

Evidence is accumulating that pituitary hormone secretion is not only regulated by feedback from hormones produced in the target organs (long feedback) on the pituitary and the hypothalamus (feedforward), but also by a feedback of the hypophyseal hormones at the hypothalamic (short feedback) and the pituitary (ultra-short feedback) level. Inhibition of thyrotropin (TSH) and MSH secretion by pituitary preparations by adding exogenous TSH or MSH to the medium was already observed in the 1960s, as was the phenomenon that adrenocorticotropic hormone (ACTH) injected in the hypothalamus lowered plasma corticosterone levels. These early observations have now been corroborated by the demonstration of the receptors for various pituitary hormones in the hypothalamus and the adenohypophysis. The thyrotropin receptor (TSHR) is found on folliculo-stellate cells in the pituitary, which are known to influence the neighboring endocrine cells. This pituitary TSR-receptor is also recognized by TSHR receptor autoantibodies, which can downregulate TSH secretion independently from thyroid hormone levels, and are therefore thought to be responsible for the frequently observed suppressed TSH levels in patients with Graves' disease who are otherwise euthyroid.

Animals↗
PubMedDate not supplied

Direct temporal-occipital feedback connections to striate cortex (V1) in the macaque monkey.

Although there have been reports of sparse projections from temporal areas TE, TF, and even TH to area V1, it is generally believed that cortical afferents to V1 originate exclusively from prestriate areas. Injections of anterograde tracers in anterior occipital and temporal areas, however, consistently produce labeled terminals in area V1. In order to confirm these results and display the full range of foci projecting to V1, we injected V1 in two monkeys with the retrograde tracer fast blue. Feedback connections were found, as expected, from several prestriate areas (V2, V3, V4, and MT). These originate from neurons in layers 3A and 6. Connections were also found from several more distal regions, namely, areas TEO, TE, TF, TH, and from cortex in the occipitotemporal and superior temporal (STS) sulci. Filled neurons occurred in two small foci in the caudal intraparietal sulcus. These more distal feedback connections tend to originate only from layer 6. An additional injection of the retrograde tracer diamidino yellow in area V2 of one animal revealed a similarly widespread network of feedback connections. In some areas (in the STS and in TEO), 10-15% of fluorescent neurons were double-labeled. These results indicate that feedback connections to early visual cortex derive from a widespread network of areas, including limbic-associated cortices. These connectional patterns testify to the massive recursiveness of anatomical pathways. As there are no reports of projections from V1 to anterior temporal cortices, our results also indicate that some cortical feedback connections may not be strictly reciprocal.

Amidines↗
PubMed2004

ERP correlates of feedback and reward processing in the presence and absence of response choice.

The feedback negativity is a component of the event-related brain potential that is elicited by feedback stimuli associated with unfavorable outcomes. The present research investigated whether this component reflects an evaluation of the valence of experienced outcomes or a process of learning about actions that led to those outcomes. The latter hypothesis predicts that the feedback negativity should be observed only when negative outcomes are experienced in relation to executed actions. Contrary to this prediction, feedback negativities were observed in simple monetary gambling tasks in which participants made no active choices (experiment 1) and no overt actions (experiment 2). However, the amplitude of the component was reduced in these tasks relative to a gambling task in which the outcomes appeared to be contingent upon participants' response choices. This reduction was correlated with changes in participants' subjective ratings of involvement in the tasks, suggesting that the evaluative process indexed by the feedback negativity is sensitive to the motivational significance of ongoing events.

Adolescent↗
PubMed1993

Influencing diagnostic and preventive performance in ambulatory care by feedback and reminders. A review.

The number of good quality studies on the effect of feedback and reminders on diagnostic and preventive activities in ambulant practice is still low. The interventions and procedures studied differ widely, and the reporting of the results is insufficiently precise. This makes comparison difficult and quantitative pooling impossible. Nevertheless, the literature supports the contention that feedback reduces the use of diagnostic tests and the costs thereby engendered. It also discloses a positive effect of feedback on the adherence of medical practice to guidelines or standards. In this respect, the effect of reminders seems to exceed that of classical methods of feedback. There is still a need for research on the effect of feedback, reminders and other instruments for quality assurance on various aspects of medical performance in different settings.

Ambulatory Care↗
PubMed2000

Influence of postal distribution of the Royal College of Radiologists' guidelines, together with feedback on radiological referral rates, on X-ray referrals from general practice: a randomized controlled trial.

BACKGROUND: The Royal College of Radiologists (RCR) have produced regularly updated guidelines on radiological referrals since 1990. A small study in 1992 showed postal distribution of guidelines reduced general practitioners' referrals over the subsequent 9 weeks. However there have been no randomized trials of the longer term effects of radiological guidelines and feedback on referral rates on X-ray requests from primary care. OBJECTIVES: To see if the introduction of radiological guidelines into general practices together with feedback on referral rates reduces the number of GP radiological requests over one year; and to explore GPs'attitudes to the guidelines. METHODS: Sixty-nine practices referring patients to St George's Healthcare Trust were randomly allocated to intervention or control groups. In February 1995 a GP version of the RCR guidelines was sent to each GP in the 33 practices in the intervention group. After 9 months intervention, practices were sent revised guidelines with individual feedback on the number of examinations requested in the past 6 months. The total number of requests per practice was compared for the year before and the year after the introduction of the guidelines. Control practices were sent the guidelines at the end of the study. All doctors were sent a questionnaire about the guidelines. RESULTS: A total of 43 778 radiological requests were made during the two years 1994-1996. In practices receiving the guidelines there was a 20% reduction in requests for spinal examinations compared with control practices (P < 0.05). This corresponded to the effect reported by GPs. There was also a 10% difference between the groups in the total number of requests made, but due to wide interpractice variation in referral rates this failed to reach statistical significance. CONCLUSIONS: Introduction of radiological guidelines together with feedback on referral rates was effective in reducing the number of requests for spinal examinations over one year. Wider use of GP-orientated guidelines with regular updating and feedback might save costs and reduce unnecessary irradiation of patients.

Attitude of Health Personnel↗
PubMed2003

Carbon metabolite feedback regulation of leaf photosynthesis and development.

Photosynthesis is regulated as a two-way process. Light regulates the expression of genes for photosynthesis and the activity of the gene products (feedforward control). Rate of end-product use down-stream of the Calvin cycle, determined largely by nutrition and temperature, also affects photosynthetic activity and photosynthetic gene expression (feedback control). Whereas feedforward control ensures efficient light use, feedback mechanisms ensure that carbon flow is balanced through the pathways that produce and consume carbon, so that inorganic phosphate is recycled and nitrogen is distributed optimally to different processes to ensure growth and survival. Actual mechanisms are sketchy and complex, but carbon to nitrogen balance rather than carbon status per se is central to understanding carbon metabolite feedback control of photosynthesis. In addition to determining the activity of the metabolic machinery, carbon metabolite feedback mechanisms also regulate photosynthesis at the leaf level through the regulation of leaf development. This review summarizes the current sketchy, but growing, knowledge of the mechanisms through which carbon metabolite feedback mechanisms regulate leaf photosynthesis.

Carbon↗
PubMed1990

Effect of feedback on learning a vertebral joint mobilization skill.

This study was designed to investigate whether concurrent quantitative feedback of performance could improve the learning of a joint mobilization technique. A group of 110 physical therapy students had been randomly divided into two groups for teaching purposes. All students had previously learned mobilization of peripheral joints and were currently learning spinal mobilization. From one of the groups, 22 students volunteered to comprise a control group, which was taught a spinal mobilization technique in the traditional way. Additional concurrent quantitative feedback of the level of force applied to the patient was given to 31 volunteers from the other group. These students formed the experimental group. A force plate was used for force measurement, and the feedback was given via an oscilloscope. The average force applied by the students' instructors was taken as an "ideal" force. The oscilloscope showed both the applied force and the "ideal" force. Consistency was measured by the variance of the group's performance. Accuracy was assessed by calculating the difference between the applied force and the "ideal" force. Results indicated that this feedback was associated with a significant improvement in accuracy and consistency in the application of the mobilizing force. This improvement was still present at a follow-up test conducted one week later. This result supports a greater use of such feedback in the teaching and practice of joint mobilization techniques, although the need for further research is emphasized.

Adult↗
PubMed2004

Prenatal programming of reproductive neuroendocrine function: the effect of prenatal androgens on the development of estrogen positive feedback and ovarian cycles in the ewe.

Exposure of the female ovine fetus to male hormones during a sensitive window of in utero life causes disruption to reproductive function. In some animals, androgen exposure completely abolishes reproductive cycles, but in others, cycles are progressively lost with age. The present study tested two predictions: that noncycling, androgenized animals are unable to respond to estrogen with a preovulatory-like surge of LH (estrogen positive feedback), and that the androgenized animals that exhibit a progressive loss of cycles also show a progressive loss of estrogen positive feedback. Androgenized ewes were generated by injection of their mothers with testosterone propionate twice per week from Day 30 to Day 90 of pregnancy (term, 147 days). Control ewes received no injections. Whether ewes could exhibit estrogen positive feedback was tested on five occasions before puberty (30 wk) and once during the anestrous period. All control animals had repeated reproductive cycles in both the first and second breeding season, and all showed robust LH surges during test periods. Despite the fact that 64% of androgenized animals showed reproductive cycles, estrogen positive feedback could be demonstrated in only 6.1% of trials. Subsequent experiments revealed that the lack of response to estrogen in androgenized animals was not because of pituitary insensitivity to GnRH, a requirement for higher concentrations of estrogen, or a surge that was delayed relative to the time of estrogen administration. The mechanisms by which some androgenized ewes can produce normal reproductive cycles in the apparent absence of estrogen positive feedback are currently unknown.

Animals↗
PubMed1987

Effects of information feedback and pulse oximetry on the incidence of anesthesia complications.

No standard outcome measures exist to evaluate the effect of interventions intended to improve the quality of anesthesia care. The authors established a clinically practical definition of outcome, and used it to assess the effect of feedback of information about complications and the effect of pulse oximetry on the rate and severity of important anesthesia-related problems encountered in the operating room (OR) and recovery room (RR). On admission to the RR, the patient's anesthetist documented Recovery-Room-Impact Events (RRIE), defined as an "unanticipated, undesirable, possibly anesthesia-related effect that required intervention, was pertinent to recovery-room care, and did or could cause at least moderate morbidity." Following a control period with no feedback of data, intense feedback of grouped (anonymous) RRIE rates was provided. Later, pulse oximeters were introduced to all anesthetizing locations. Among 12,088 patients (71% of all RR admissions), 18% had at least one RRIE in the OR or RR. The most common RRIEs were hypotension (4.4%), arrhythmia (3.9%), hypertension (1.5%), intubation difficulties (0.8%), hypoventilation (0.8%), and hypovolemia (0.6%). Feedback of information produced no demonstrable change in the rate of RRIEs. Although significantly fewer patients experienced RRIEs (15.6% vs. 12.4%, P less than 0.0001), hypotensive RRIEs (5.2% vs. 3.8%, P = 0.0003), and hypovolemic RRIEs (0.88% vs. 0.42%, P = 0.0017) following the introduction of pulse oximetry in the OR, confounding factors prevent establishment of a cause-and-effect relationship. Quality assurance may require more direct intervention and individual feedback to be effective. Still, the RRIE measure requires minimal effort at low cost and encourages improved transmission of information at the time of admission to recovery-room care.

Anesthesia↗
PubMed2003

Responses of rural family physicians and their colleague and coworker raters to a multi-source feedback process: a pilot study.

PURPOSE: To describe responses of family physicians, their medical colleagues, and coworker raters to a multisource feedback assessment process. METHOD: Data collection tools included multisource feedback self-assessment and medical colleague, coworker, and patient rating forms; and program evaluation physician and rater questionnaires. RESULTS: The pilot study included 142 physicians and their raters, with 113 (80%) physicians completing evaluations. Positive correlations were found between familiarity scores and medical colleague and coworker mean ratings. Peer medical colleagues were significantly more familiar with physicians than were consultants. Consultants were unable to rate items most frequently. Physicians disagreed with colleague feedback more frequently. Agreement was positively correlated with scores. CONCLUSIONS: Familiarity, ability to observe physicians appropriately to rate them, and physicians' responses to feedback are factors to consider when multisource feedback is used.

Adult↗
PubMed1999

Enhancement of left-right sensorimotor EEG differences during feedback-regulated motor imagery.

EEG feedback studies demonstrate that human subjects can learn to regulate electrocortical activity over the sensorimotor cortex. Such self-induced EEG changes could serve as control signals for a Brain Computer Interface. The experimental task of the current study was to imagine either right-hand or left-hand movement depending on a visual cue stimulus on a computer monitor. The performance of this imagination task was controlled on-line by means of a feedback bar that represented the current EEG pattern. EEG signals recorded from left and right central recording sites were used for on-line classification. For the estimation of EEG parameters, an adaptive autoregressive model was applied, and a linear discriminant classifier was used to discriminate between EEG patterns associated with left and right motor imagery. Four trained subjects reached 85% to 95% classification accuracy in the course of the experimental sessions. To investigate the impact of continuous feedback presentation, time courses of band power changes were computed for subject-specific frequency bands. The EEG data revealed a significant event-related desynchronization over the contralateral central area in all subjects. Two subjects simultaneously displayed synchronization of EEG activity (event-related synchronization) over the ipsilateral side. During feedback presentation the event-related desynchronization/event-related synchronization patterns showed increased hemispheric asymmetry compared to initial control sessions without feedback.

Adult↗
PubMed1982

The effect of concurrent feedback in reducing inappropriate hospital utilization.

This study conducted in four general hospitals, evaluates the effectiveness of feedback from utilization review coordinators in reducing the number of inappropriate hospital days. Experimental control was exerted over the type of feedback provided in the utilization review process to produce four treatment groups (including a control group) that vary according to 1) the channel used to inform an attending physician of a probable inappropriately located patient and 2) the amount of discretion permitted the nurse coordinator in deciding whether, when and to whom this information is provided. The results of the study indicate that physician and hospital performance in utilization review, measured both by inappropriate patient days and length of stay, are affected by the feedback strategy employed. For patients inappropriately located for a portion of their hospital stay, provision of concurrent feedback resulted in reduction of approximately two thirds of an inappropriate day and two and one half total days, compared with patients for whom no feedback was provided or for whom physician advisor involvement was required. In addition, the effect of reasons causing patients to be inappropriately located (barriers) was assessed. Barriers outside the realm of influence of the hospital or the physician were found to impede the effectiveness of the utilization review systems.

California↗
PubMed1984

Improving physician performance through peer comparison feedback.

A project to improve physician performance in colorectal cancer screening was evaluated as part of an ambulatory quality assurance program. A minimum standard was adopted requiring a digital examination and stool test for occult blood at annual check-ups of patients aged 40 years and older. During a 31/2-year period, three different intervention strategies for improved compliance with the standard were sequentially implemented and assessed: educational meeting, retrospective feedback of group compliance rate, and retrospective feedback of individual compliance rate compared with that of peers. A pretest/posttest design was employed in evaluating the first two intervention strategies. Neither strategy resulted in significant improvement in compliance. Monthly feedback of individual performance ranked with that of peers was then implemented in a randomized clinical trial utilizing a crossover design. During the first 6-month period, the physicians receiving feedback (group 1) improved from 66.0% to 79.9% (P less than 0.001), while the control group (group 2) also improved, from 67.5% to 76.6% (P less than 0.001), suggesting a spillover effect. During the second 6-month period, group 2 received feedback and group 1 did not. Group 1 stabilized at approximately 80% while group 2 continued to improve from 76.6% to 84.0% (P less than 0.001). Behavior changes persisted at 6 and 12 months after intervention.

Boston↗
PubMed1999

The effect of panel membership and feedback on ratings in a two-round Delphi survey: results of a randomized controlled trial.

BACKGROUND: Past observational studies of the RAND/UCLA Appropriateness Method have shown that the composition of panels affects the ratings that are obtained. Panels of mixed physicians make different judgments from panels of single specialty physicians, and physicians who use a procedure are more likely to rate it more highly than those who do not. OBJECTIVES: To determine the effect of using physicians and health care managers within a panel designed to assess quality indicators for primary care and to test the effect of different types of feedback within the panel process. METHOD: A two-round postal Delphi survey of health care managers and family physicians rated 240 potential indicators of quality of primary care in the United Kingdom to determine their face validity. Following round one, equal numbers of managers and physicians were randomly allocated to receive either collective (whole sample) or group-only (own professional group only) feedback, thus, creating four subgroups of two single-specialty panels and two mixed panels. RESULTS: Overall, managers rated the indicators significantly higher than physicians. Second-round scores were moderated by the type of feedback received with those receiving collective feedback influenced by the other professional group. CONCLUSIONS: This paper provides further experimental evidence that consensus panel judgments are influenced both by panel composition and by the type of feedback which is given to participants during the panel process. Careful attention must be given to the methods used to conduct consensus panel studies, and methods need to be described in detail when such studies are reported.

Attitude of Health Personnel↗
PubMed2006

Self-rated breast cancer risk among women reporting a first-degree family history of breast cancer on office screening questionnaires in routine medical care: the role of physician-delivered risk feedback.

PURPOSE: We investigated whether risk-related feedback delivered by one's primary care physician is associated with self-ratings of risk among women found to have a first-degree family history of breast cancer on office screening questionnaires. METHODS DESIGN: Mailed survey of women registered with the Cancer Genetics Network having a first-degree family history of breast cancer. Eligibility: Completion of primary care-based family history screening within the past year. INDEPENDENT VARIABLE: presence of physician feedback about breast cancer risk. Dependent variable: self-rated breast cancer risk. Modifying variable: trust in one's doctor. RESULTS: Three hundred one women met eligibility criteria (73% minimum response rate); feedback was associated with rating one's risk to be "high" in both crude and multivariate analysis. (ORadj = 2.38; 95% CI = 1.30, 4.38). Higher levels of trust in the physician were associated in a dose-dependent fashion with the strength of association between feedback and self-rating one's risk to be high. CONCLUSIONS: Physician feedback following the identification of a first-degree family history of breast cancer appears to influence whether or not women categorize themselves to be at high risk and trust is an important modifier of this association.

Adult↗
PubMed2004

Effects of nonlocal feedback on traveling fronts in neural fields subject to transmission delay.

The work introduces a model for reciprocal connections in neural fields by a nonlocal feedback mechanism, while the neural field exhibits nonlocal interactions and intra-areal transmission delays. We study the speed of traveling fronts with respect to the transmission delay, the spatial feedback range, and the feedback delay for general axonal and feedback connectivity kernels. In addition, we find a novel shape of traveling fronts due to the applied feedback and criteria for its occurrence are derived.

Action Potentials↗